kirenol and pimarane

Kirenol is one of the biologically active diterpenoids from Siegesbeckia pubescens. In terms of the high content and typical structure, many ent-diterpenoids separated from S. pubescens were presumed to be biologically related to kirenol. Among them, epoxy-pimarane diterpenoids are belonging to a special family of naturally occurring compounds that attracted our attentions on their putative biosynthesis pathway and biological activities. Here, we designed and synthesized two known 14,16-epoxy-pimarane diterpenoids (2 and 3) and five 8,15-epoxy-pimarane diterpenoids (4-8) from kirenol. Their absolute structures were determined by 1D and 2D NMR data and the absolute configurations of 4 were confirmed by X-ray crystallographic data. Their inhibition effects on factor Xa (FXa) were evaluated to assess the potentiality of epoxy-pimarane diterpenoids as FXa inhibitor agents.

Topics: Abietanes; Crystallography, X-Ray; Diterpenes; Dose-Response Relationship, Drug; Epoxy Compounds; Factor Xa; Factor Xa Inhibitors; Humans; Molecular Structure; Structure-Activity Relationship

Phytochemical investigation of the above-ground parts of Siegesbeckia pubescens yielded 25 diterpenoids, including five new ent-pimarane diterpenoids (1-3, 11, and 12) and four new ent-kaurane diterpenoids (13-16). The structures and relative configurations of the new compounds were elucidated by comprehensive spectroscopic analysis and by comparison of their NMR data with those of related compounds. Single-crystal X-ray diffraction analysis confirmed the structures of 8, 13, and 14. Seven of these diterpenoids were evaluated for cytotoxic activity against HSC-T6, HeLa, and B16 cell lines. Compounds 11 and 14 exhibited moderate cytotoxicity.

Topics: Abietanes; Antineoplastic Agents, Phytogenic; Asteraceae; Crystallography, X-Ray; Diterpenes, Kaurane; Drug Screening Assays, Antitumor; Drugs, Chinese Herbal; Humans; Molecular Conformation; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular